1. Field of the Invention
The present invention relates to a transfer apparatus which displays an image recorded in digital form by a digital still camera (DSC), a video camera, a personal computer or the like through a transmission type image display device formed by a liquid crystal display device (LCD), and transfers the displayed image to a photosensitive recording medium such as an instant photographic film which develops color by light, thereby forming an image.
2. Description of the Related Art
Conventionally known examples of a method for transferring (i.e., printing) or recording a digitally-recorded image to or on a photosensitive recording medium include an ink jet system using a dot-type printing head, a laser recording system, and a thermal recording system.
A printing system like the ink jet system has various problems. For example, printing takes time, ink is likely to cause clogging, and precision printing results in the sheet being moistened by ink. The laser recording system involves an expensive optical component such as a lens, resulting in high apparatus cost. Further, the laser recording system and the thermal recording system require considerable power consumption, and are not suited to be carried about.
Thus, generally speaking, the transfer apparatuses used in these systems and, in particular, the ones used in the ink jet system have a problem in that the more precise the apparatus, the more complicated the driving mechanism and the control mechanism, and the larger and the more expensive the apparatus, printing taking a lot of time.
In this regard, JP 10-309829 A and JP 11-242298 A disclose transfer apparatuses of the type in which a display image is formed on a photosensitive recording medium like an instant film by using a liquid crystal device, thereby achieving simplification in structure and a reduction cost.
The electronic printer disclosed in JP 10-309829 A is capable of copying the display screen of a liquid crystal display on a photosensitive medium to produce a hard copy of a quality equal to that of a photograph. However, in order to copy the display screen of the liquid crystal display on the photosensitive medium in this electronic printer, an optical component such as a rod lens array is arranged between the display screen of the liquid crystal display and the photosensitive medium, so that a predetermined distance (total conjugate length) is required between them. In the example shown, the requisite distance is 15.1 mm. Further, the optical component is rather expensive.
In the case of the transfer apparatus disclosed in JP 11-242298 A, there is no need to use an expensive optical component such as a lens or to secure an appropriate focal length. Thus, as compared with the conventional transfer apparatuses, a further reduction can be achieved in terms of size, weight, power consumption, and cost. As shown in FIG. 7, a photosensitive film 400 is closely attached to the display surface of a transmission type liquid crystal display (hereinafter referred to as LCD) 300, and a light source (back light 100) provided on the opposite side of the photosensitive film 400 with respect to the LCD 300 is turned on. That is, a fluorescent lamp 101 is switched on to turn on the back light, whereby the image displayed on the LCD 300 is transferred to the photosensitive film 400.
Further, as shown in FIG. 8, the above-mentioned publication discloses another-embodiment, according to which a lattice 200 is provided between the back light 100 and the LCD 300, whereby diffusion of light from the back light 100 is restrained. That is, the light is approximated to parallel rays. Further, by providing a spacer 201 consisting of a rectangular hollow member between the lattice 200 and the LCD 300, it is possible to prevent the image of the frame of the lattice 200 (the shadow due to the frame) from being taken by the photosensitive film 400, thus improving the clarity of the image formed on the photosensitive film 400 to a satisfactory degree from the practical point of view without providing an optical component or securing an appropriate focal length.
Further, as shown in FIG. 7, the publication discloses an example of a transfer apparatus in which the thickness of the LCD 300, that is, the sum total of the thicknesses of the following components: a polarizing plate 301 on the display surface side, a glass substrate 302, a liquid crystal layer 303, a glass substrate 304, and a polarizing plate 305 on the back light 100 side is 2.8 mm and in which the image on the screen of the LCD 300 with a dot size of 0.5 mm is transferred to the photosensitive film 400. To prevent diffusion of the light from the LCD 300, there is provided a 5 mm lattice with a thickness of 10 mm, and a 20 mm spacer 201 is arranged between the lattice 200 and the LCD 300. Further, the LCD 300 and the photosensitive film 400 are closely attached together to effect image transfer without involving blurring (unclarityl of the image.
In this case, an image displayed with a dot size of 0.5 mm is transferred with an enlarge dot size of up to 0.67 mm, which means an enlargement by approximately 0.09 mm on one side, and yet the image obtained is satisfactory from the practical point of view.
As described above, in the transfer apparatus disclosed in JP 11-242298 A, image transfer is effected, with the liquid crystal display (LCD) and the photosensitive film being closely attached together, to prevent blurring (unclarity) of the image and to obtain an image satisfactory from the practical point of view. It is to be noted, however, that exposure of the photosensitive film in this arrangement involves the following problems.
First, as shown in FIG. 7, on the outermost surface of the LCD 300, there is arranged the film-like polarizing plate 301, which is closely attached to the photosensitive film 400 during exposure. When the photosensitive film 400 is moved to perform a post-processing, the photosensitive film 400 and the polarizing plate 301 are rubbed against each other to thereby flaw the film-like polarizing plate 301, and the flaw on the polarizing plate 301 is transferred to the photosensitive film 400. Further, this flaw causes scattering of light, resulting in deterioration in the image quality.
It might be possible for the polarizing plate and the photosensitive film to be closely attached together during exposure and slightly spaced apart from each other when the photosensitive film is moved. For this purpose, however, it would be necessary to provide, apart from the photosensitive film moving mechanism, a mechanism for effecting close attachment and detachment of the photosensitive film, which is contradictory to the requirement for a reduction in cost and size.
Further, generally speaking, a photosensitive film, for example, an instant film, which is the easiest to use, is kept in a lightproof case until it is loaded in a transfer apparatus. Since this lightproof case is equipped with an opening frame somewhat larger than the film, the following procedures must be followed before the photosensitive film can be brought into close contact with the polarizing plate.
First, prior to exposure, one photosensitive film is extracted singly from the lightproof case, and brought into close contact with the surface of the polarizing plate on the surface of the LCD. In this condition, exposure is performed, and, after the completion of the exposure, the photosensitive film is separated from the polarizing plate surface, and moved for a next processing (In the case of an instant film, a processing liquid tube provided in the film sheet is pushed open).
These procedures must be repeated for each photosensitive film. In particular, separating the photosensitive film from the polarizing plate surface does not square with automation (or mechanization).
Recently, the screens of LCDs have progressed in terms of definition, and LCDs with an increased number of pixels and a smaller dot size are being commercialized. For example, as LCDs using low-temperature polysilicon type TFTs, UXGA (10.4 inches; 1200×1600 pixels), XGA (6.3 and 4 inches; 1024×768 pixels) are on the market.
An attempt to apply an LCD with such a high-definition screen to the transfer apparatus disclosed in JP 11-242298 A would lead to the following problem. In the case of UXGA, the dot size of each of the RGB pixels is approximately 0.04 mm on the shorter side. In a transfer apparatus as disclosed in the above-mentioned publication, in which enlargement in dot size is involved, it would be impossible to transfer an LCD image of such a minute dot size to a photosensitive film with satisfactory clarity in a condition in which the dots of the RGB pixels are clearly distinguishable.